Animal and human tumors contain peptide-lipid complexes tentatively classified as proteolipids. There are two types of proteolipids. Proteolipid isolated from Walker Carcinosarcoma 256 (W-256) designated as neoproteolipid-W (NPL-W), contains neutral glycosphingolipids, and proteolipid isolated from Morris hepatoma 5123 (MH), designated as neoproteolipid-S (NPL-S), contains gangliosides. In blood serum of MH-bearing rats there is a 7-fold increase of NPL-S levels as compared with controls. There is also a substantial alteration of serum gangliosides: 4-fold increase of monosialogangliosides and disialogangliosides and 3-fold decrease of trisialogangliosides. In W-256-bearing rats, NPL-W appears in measurable quantities in serum and in even larger quantities bound to erythrocytes. The effect of W-256 upon blood serum gangliosides is less pronounced than in MH-bearing rats. Most likely, the neutral glycosphingolipid profile is more affected in the case of an "NPL-W type" tumor. The presence of neoproteolipids was demonstrated also in blood sera of cancer patients with advanced forms of cancer. The general objectives of this project are: 1) To elucidate the effect of malignancy (selected transplanted tumors and human tumors of NPL-S and NPL-W types) upon serum ganglioside, neutral glycosphingolipid profiles, and NPL-S and NPL-W levels; 2) To elucidate how early the significant alterations of the above mentioned lipids in serum occur with the growth of transplanted tumors; 3) On the basis of (1) and (2) to select the most specific alterations in glycosphingolipid patterns in order to test them as a tool for the earlier detection of cancer and as a tool for the evaluation of the efficacy of cancer treatment, and (4) to complete the biochemical characterization of neoproteolipids.